This invention concerns a process for the preparation of synthetic, linear, fiber-forming polyamides in the presence of a phenylphosphinate, a cupric salt and a specified ratio of KBr and KI.
The stabilization of polyamides against embrittlement by preparing them in the presence of certain phosphorous, copper and halogen compounds is disclosed in U.S. Pat. No. 2,705,227 to Stamatoff. However, under normal conditions, e.g., continuous polymerization including a flasher stage, this combination of additives results in the formation of metallic copper during the polymerization, resulting in processing difficulties and a reduced copper concentration in the final polymer.
An object of this invention is to reduce the amount of copper loss under such conditions, thus minimizing the problems associated therewith while otherwise retaining the beneficial properties of the resulting products and improving the process economics.